CA 195 is a tumor associated antigen which is identified by means of a monoclonal antibody, CC3C195 (Bray et al., 1987). Normal subjects show very low or undetectable serum CA 195 levels by the currently utilized radioimmunometric method (Gupta et al., 1987; Sundaram et al., 1987; Bhargavva et al., 1987). However, elevated levels are often found in patients with pancreatic, gastric, liver, colorectal and other gastrointestinal malignancies (Bhargava et al., 1987). Sundaram et al., (1987) found CA 195 to be superior in the identification of colon cancer to the classically utilized tumor marker CEA. Serum levels are primarily used for prognosis and progress of the disease. Although the marker shows less utility in the diagnostic phase, it is still used as an adjunct tool. Hybritech Inc. developed a radioimmunoassay for the identification of the antigen utilizing membranes from a human colon tumor. This radioimmunoassay is commercially available through Hybritech Inc. Calibrators and controls for this assay can be obtained from various malignant tissues or a human colon cancer cell line (Fukuta et al., 1987). However, human cancerous tissue is difficult to obtain, costly, and poses numerous safety problems. Obtaining the CA 195 from human cell lines requires tissue culture facilities, presents safety problems, is costly, and relatively small quantities are obtained.
This invention relates to the identification of an CA 195-like material in human amniotic fluid. This material is present in amniotic fluid in a much higher level than that in normal human serum and can be isolated without encountering the difficulties of handling the other human materials. The identification of the CA 195-like material in amniotic fluid has lead to the ability to isolate a material which is much less expensive to produce than the previous materials and methods and which appears to be as useful as the previous materials.
The invention covers not only the identification of the material but also techniques for isolation and use of the CA 195-like material.